ANRATOR EXHAUST SIGNATURE SUPPRESSION (ESS) SYSTEM MO 0/TING ETC(U)
7ENERATO EXHA UST SINC G NATREAN SUPPRESS I ON(ES SY STE MONTN /2CU
JUN 80 R E WALLACE DAAK70-79-C-0207
UNCLASSIFIED T0-75297 NL
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Report TD 75297 LY ~c
GENERATOR EXHAUST SIGNATURE SUPPRESSION (GESS) SYSTEM MOUNTING..ADAPTERS FOR THE 15 KW AND 30 KW DOD DIESEL ENGINE GENERATORS
00
Robert E. WallaceVaro, Inc.
00 Texas Division0 2201 Walnut StreetGarland, Texas 75040
June, 1980
Final Report
Distribution of this document is unlimited
Prepared. for:
U.S.A. MERADCOM, ATTN; DRDME-RT (T. Steck)Camouflage and Topographic LaboratoryFort Belvoir, Virginia 22060
i 80 9 17 02
7. NM 7-=
The views, opinions, and/or findings contained in the reportare those of the author and should not be construed as anofficial Department of the Army position, policy, ordecision, unless so designated by other documentation.
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Report TD 75297
GENERATOR EXHAUST SIGNATURE SUPPRESSION (GESS) SYSTEM MOUNTINGADAPTERS FOR THE 15 KW AND 30 KW DOD DIESEL ENGINE GENERATORS
Robert E. WallaceVaro, Inc.Texas Division2201 Walnut StreetGarland, Texas 75040
June, 1980
Final Report
Distribution of this document is unlimited
Prepared for:
U.S.A. MERAVCOM, ATY i DRDME-RT (T. Steck)Camouflage arid Topograpnic LaboratoryFort Belvoir, Virginid 22060
14
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Block 20 continued:
This report describes the design of these adapters. Thesmaller adapter ("A" adapter) was patterned after onesupplied by MERADCOM with two essential features: mountingto the generator without generator modification except theremoval of small parts (bolts and the weather cap on theexhaust pipe), and provision of a lip on which to rest theGESS duct while it is being mounted. Adapter weight was tobe less than 12kg.
The second ("B") adapter was experimental in nature, but wasto mount the GESS duct in a down-tilted attitude so that nohot interior parts of the duct can be seen above a horizon-tal plane through the tip of the GESS duct.
Both adaptecs were to be inculated for thermal and acousticeffect.
This design effort produced two adapters satisfying theabove requirements. The 8.6 kg weight of the A adapter was28% less than the 12kg goal. Acoustic testing demonstratedthat use of the adapters is acoustically compatible with theGESS System. Noise levels were measured at 25 feet from thegenerator exhaust end at 76.7 dBA - well below the 80 dBAlimit presented in the Purchase Description for theseadapters.
No thermal suppression tests were performed to assess theadapters effect thermally.
\I Aioesion For "
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SUMMARY
The purpose of the work described in this report was to
develop two adapters which make it possible to use the
Generator Exhaust Suppression System (GESS) on 15kw and 30kw
generators which have the same external configuration. One
adapter (called the "A" adapter) was to be a refinement of a
pattern adapter supplied by MERADCOM retaining two of its
essential features: mounting to the generator without
generator modification except the removal of small parts
(bolts and the weather cap on the exhaust pipe), and
provision of a lip for resting the GESS duct on to assist in
GESS duct mounting. Adapter weight was to be less than
12kg.
The second adapter was experimental in nature, but was to
mount the GESS duct in a down-tilted attitude so that no hot
interior parts of the duct can be seen above a horizontal
plane through the tip of the GESS duct. It was known as the
"B" adapter.
Both adapters were to be insulated for thermal and acoustic
effect.
This design effort produced two adapters satisfying the
above requirements. The 8.6 kg weight of the A adapter was
28t less than the 12kg goal. Acoustic testing demonstrated
that use of the adapters is acoustically compatible with the
GESS System. Noise levels were measured at 25 feet from the
generator exhaust end at 76.7 dBA - well below the 80 dBA
limit presented in the Purchase Description for these
adapters.
No thermal suppression tests were performed to assess the
adapters effect thermally.
I1
PREFACE
The work described here for adapters design and construction
was authorized under Contract DAAK70-79-C-0207 from the
Mobility Equipment Research and Development Command
(MERADCOM). This adapters design work is associated with
the continuing efforts which Varo has been involved with in
design of generator thermal suppression devices andequipment. Preliminary work in duct design related to the
Generator Exhaust Signature Suppressor (GESS) duct occurred
in 1976 during development of equipment for the MALOR Mortar
Locating Radar (now FIREFINDER) system und r contract
DAAG53-76-C-0099 in 1976. Work on a small adapter to make
the GESS duct fit 15 and 30 kw generators took place under
contract DAAK70-77-M-3727, but its use did not remove the
requirement to modify the generator for GESS attachment.
In 1978, two GESS ducts were made after minor design changes
enhance producibility, under contract DAAK70-77-M-4895. It
was this form of GESS duct upon which adapters design was
based for the work being reported on here.
Apart from contracts with Varo, Inc., Texas Division as
above, work related to this effort took place in 1978 for
noise suppression of diesel generators under MERADCOM
contract DAAG53-76-C-0169 to Industrial Acoustics Co., Inc.
The noise control kit for 15kw and 30kw diesel generators
which resulted from that work incorporated the GESS system.
The pattern adapter upon which the A adapter refinement here
was based was also generated under that contract and thetest generator supplied to Varo for adapters development was
one modified with the noise control treatment from
Industrial Acoustics.
2
Varo wishes to acknowledge the overall guidance for these
adapters development which was provided by Mr. Thomas T.
Steck of MERADCOM. Mr. R. H. Ldughlin of Varo monitored the
development and Mr. Harry Loveless performed the detail
design of the adapters under the guidance of the author and
Mr. Laughlin.
3
TABLE OF CONTENTS
Page
SUMMARY 1
PREFACE 2
1.0 INTRODUCTION 5
2.0 INVESTIGATION 8
2.1 Adapter A Design 8
2.1.1 Goals for Adapter A 8
2.1.2 Adapter A Description 8
2.1.3 Strengthening and Lightening 10
2.1.4 Fastening 12
2.1.5 Size Reduction 13
2.1.6 Thermal Effects and Considerations 13
2.2 Adapter B Design 19
2.2.1 Goals for Adapter B 19
2.2.2 Description of Adapter B 20
2.3 Exhaust Extensions for Use with Adapters A and B 23
2.4 GESS Duct Design Modifications for 25
Compatibility with Adapters
2.5 GESS Blanket Design 26
2.5.1 GESS Blanket and Duct Jacket Changes 26
2.5.2 B Adapter Jacket Design 28
2.6 Acoustic Testing 29
3.0 DISCUSSION 34
4.0 CONCLUSIONS 36
5.0 RECOMMENDATIONS 37
4
r .r.- MAW
1.0 INTRODUCTION
This effort was directed at the goal of providing adapters
for the 60kw Generator Exhaust Suppression System (GESS) to
make it suitable for use with 15/30kw generators of the
PATRIOT Air Defense Missile System. Two forms of adapters
were developed - one for the main objective of coupling the
GESS duct onto 15/30kw generators and the second to tip the
duct down until the exposure of hot areas through the
louvered opening is reduced to 0* above the horizontal.
A pattern model for the first adapter was supplied by
MERADCOM which had two features which were specifically
called out for inclusion in the new adapter patterned after
it. They were (1) that the adapter require no drilling of
holes in the generator or removal of anything but bolts in
order to install the adapter, and (2) the inclusion of a lip
at the bottom of the adapter upon which to rest the GESS
while attaching it to the adapter after the adapter had been
bolted onto the generator.
An adapter which simply permitted the GESS duct to be
mounted on 15 or 30kw generators without leakage of hot air
had been designed and built in 1978, but despite the small
size and weight (about 35 inches x 8 inches and about 2 kg),
it was judged to be unsatisfactory because it did not
alleviate the requirement that generators on which the GESS
would be used have holes drilled in them and the grill
removed. That was deemed unacceptable due to the great
I reluctance of users to make any permanent modifications such
as hole drilling.
q 5
In addition loss of the grill once removed was felt to be
probable so that if the user wanted to restore the generator
to the original condition, not wanting to use the GESS, he
might find himself lacking a grill.
The Pattern adapter from MERADCOM overcame those objections
and also provided a convenient lip upon which to rest the
GESS duct (weighing 36 kg) while attaching it to the
adapter. It, however, lacked mechanical strength in some
places, was wider than necessary, and did not have any
insulation inside the frame. Hot air leakage was also noted
from several places as will be discussed in Section 2.0.
This design effort was therefore authorized to improve thedesign of this adapter while retaining the two features
mentioned above.
The resulting adapter is referred to hereafter in this
report as the "A" adapter. The second adapter has the
purpose of tipping the GESS duct down so that the opening
for exhausts exit cannot be seen above a horizontal plane
through the tip of the GESS. This adapter is hereafter
referred to as the "B" adapter. It was to mount to the "A"
adapter and permit GESS mounting in the desired orientation
to reduce angular exposure of the inside of the GESS duct to
horizontal viewing or below.
The two adapters are schematically represented in side view
in Figure 1.
The adapters project effort can be broken down into four
basic parts: hardware design, hardware fabrication,
adapters testing (fit, attachment, acoustic), and report
writing.
6
96
T- - -- - - - - - - -~------.-----.--------.--~---------
Generator
B adapter
A adapter
Generator
horizontal
532
Figure 1. GESS Attachment to I15KW or 30KW Generators with Adapters A and B,
7
2.0 INVESTIGATION
2.1 Adapter A Design
2.1.1 Goals for Adapter A
The basic assumptions under which Adapter A was designed
were mechanical and functional. As already mentioned it was
to be mountable without modification to the generator (i.e.
- no holes could be drilled in the generator nor could the
grill be removed). The lip at the bottom of the pattern
adapter was a requirement to assist during attachment of the
GESS duct. A goal was set that Adapter A weigh less than 12
kg and that it be stronger than the pattern adapter.
Insulation was also to be added for thermal and acoustic
effect. Although thermal testing of the adapters was not in
the scope of the contract, design attention was given to
incorporating thermal insulation features of the GESS system
into the adapters so that the adapter mounted GESS duct
would function acceptably from a thermal standpoint.
2.1.2 Adapter A Description
The adapter which resulted from design to the above goals is
shown in Figure 2 bolted onto the 15kw generator supplied to
Varo for research. The grill does not have to be removed
nor anything but bolts and the exhaust pipe weather cap
removed for its installation. The resting lip is seen atthe bottom and the latching system (the catch halves) at the
side. The adapter was insulated around the sides and at the
back of the top and across the top.
8
I , Figure 2. Completed A Adapter Mounted on a I15KW Generator
9
The frame of the adapter is 2.75 inches wide and the total
weight (excluding the exhaust extension) is 8.6 kg, 28%
lighter than the limit weiqht of 12 kg set as a goal.
Figure 3 shows the GESS duct mounted on the 15kw generator
with the Adapter. Blanket insulation which would normally
cover the adapter and generator is left off to show the
adapter-GESS duct relationship.
Paragraphs to follow describe design aspects of the Adapter.
2.1.3 Strengthening and Lightening
Since the pattern adapter was made from steel, it was felt
that strengthening and lightening could be accomplished by
making the material choice of aluminum for the construction
with thicker sections and gusseting. The deflection of
beams is inversely proportional to the product of modulus of
elasticity and the moment of inertia for the beam. But the
moment of inertia is proportional to the height of the beam
cubed. Therefore by making a beam thicker, the bending
resistance rapidly becomes greater (with the cube of
thickness). Aluminum is not as strong as steel (its modulus
is just about 1/3 the value for steel), but the bend
resistance loss incurred by going to aluminum can be readily
compensated for by increasing thickness. Aluminum members
made-Y,3/ = 1.44 thicker than steel counterparts
(so that (thickness alum/thickness steel)3 = 3) should
resist bending equally as well. Therefore by making the
parts roughly half again as thick, but of aluminum rather
than steel, the resulting part has about the same strength.
Aluminum being only 1/3 the weight of steel thus yields
equivalence in strength at roughly half the weight provided
the thickness of sections is increased by about 1.5.
10
II
I
11
It had been noted when bolting the pattern adapter onto the
generator that deflection of the mounting flange occurred.
It was bent toward the front of the generator by the pull of
the mounting bolt with the sealing gasket being by necessity
several inches away. Therefore it was elected to place
flange gussets near the upper and lower mount holes to help
strengthen the mount flange. In addition and to helpprevent overcompression of the sponge rubber gasket, spacerswere placed on the mounting flange to limit the closure of
the gap between the mount flange and the face of the
generator. The spacers are designed to permit a maximum of
0.090 inch gasket compression. The use of these spacers had
an unanticipated benefit it seemed in mounting the adapter.
Without the spacers it was noted that the fasteners were
very hard to turn for attaching the GESS to the adapter.
Once the spacers were installed the force for fastening the
GESS duct was greatly reduced to the planned level. That is
attributed to the removal of adapter distortion induced by
uneven tightening of the mount bolts without the spacers on
the adapter.
2.1.4 Fastening
The fastener which was selected for the A adapter and B
adapters was the same one formerly used with the GESS. No
dissatisfaction with its performance had been noted earlier
and tne quick release feature it lends was still thought to
be desirable. This is the Simmon's "Link Lock" fastener
with a spring force take-up to limit the clinch force to 80
lbs (unless bottomed out).
Gasket material was 3/8 thick x 1 inch wide silicone rubber
sponge strips. They were attached to the adapters with Dow
Corning RTV 732 adhesive/sealant. The surface of the
12
A __ __ _
aluminum to which the gasket was to be applied was kept free
of paint and cleaned with acetone as was the mating surface
of the sponge gasket material.
2.1.5 Size Reduction
The pattern adapter was 3.88 inches thick with a 2 inch lip
at the bottom. Conceptual attempts were made to compress
the thickness of the adapter to less than an inch, but to do
so would have required significant changes to the GESS duct.
The internal bracing (channel braces just inside the back
frame of the GESS duct) would have to have been curved so
that they would not contact the radiator grill of the
generator and the GESS duct itself would require slotting at
the bottom to clear the grill side members. In particular,
the latter modification was undesirable due to the potential
for malfunction of the GESS duct due to leaking hot gases
from the slot. To avoid this difficulty, it was necessary
to make adapter A 2.75 inches wide, but that is still a 30%
reduction in width of the adapter. Some minor changes to
the outside of the GESS are still required due to the
fastening catch location on the adapter being closer to the
duct than formerly the case. They were deemed acceptable to
keep the adapter as thin as possible since the GESS duct is
not in production.
2.1.6 Thermal Effects and Considerations
The primary function of the GESS system is that it provide
exposed surface temperatures which are near ambient levels.
Preliminary investigative testing revealed that the pattern
adapter had temperatures 100 to 250 C greater than on
parallel GESS metal surfaces. Insulating the adapters was a
13
A 11
requirement of the contract at the beginning and this result
supported the requirement. Because the GESS duct is already
insulated and the thermal load from exhaust gases was
anticipated to be similar, the same insulation thickness and
type was selected for the adapters. That insulation was a
silica/alumina ceramic fiber batt with good insulating
performance and good acoustic absorption. It was retained
in the adapter with 20 gage perforated aluminum sheet (50%
open) riveted onto one inch thick spacers, the same type
retaining as for the GESS.
These spacers which hold the perforated inner skin in place
over the insulation were made of fiber glass reinforced
plastic (FRP) chosen over aluminum because of the difference
in tnermal conductivity. Aluminum has a conductivity about
60 times higher than the value given for the FRP spacers.
Another thermal factor which was examined was the sealing of
the adapter to the generator and to the GESS duct. Since a
preliminary adapter was supplied by MERADCOM as a pattern,
it was available for leak testing. It was mounted to the
generator and the GESS duct attached and the generator
started and run in different conditions of louver opening.
These louvers control the cooling air flow depending on
coolant temperature. They are opened automatically during
normal operation of the generator as it warms to operating
temperature, by means of a linkage.
Leakage was noted from slots at the bottom of the adapter
(which are necessary to clear the side members of the
radiator grill) once the louvers had opened roughly
one-third or more. From the closed position to about 1/3
open, outside air was drawn in through the slot openings due
14
to the creation of a region of negative pressure inside the
adapter/duct system at the slots. Since hot air ejectionfrom the slots was pronounced with the louvers open full(condition of hottest exhausts through the GESS duct), it
was regarded as important that this leak be treated in the
new adapter design. It was determined that elimination of
the slots was not possible in the new adapter as a solution
to this leakage. A workable solution was to attach a
rubberized fiberglass fabric patch across slots also
provided in the new adapter. Figure 4 is a photograph of
the bottom of the new adapter with the slot on the left side
extending through the frame up to the lip angle at the back.
Figure 5 shows the rubberized fiber glass fabric patch in
place of over one slot with the adapter mounted on the
generator. Because the fabric is both thin and flexible to
some extent, it permits the adapter to be slid in with the
slots around the side members of the grill and the patch
passing under the grill side members back to the gasket.
Leak testing after completion of the adapter demonstrated
successful prevention of leakage from the slots by this
method.
Another leak source was discovered at the same time at the
upper row of mounting holes in the adapter. The gasket line
between the pattern adapter and the generator was just below
that row of mount holes. Oversize holes in the adapter (to
accomodate differences in hole patterns between different
generators probably) were not filled by the bolt neads used
i to mount the adapter and hot air escaped out these holes.
It would contribute unnecessarily to heat load on the bottom
of the blanket just above that position when the blanket is
attached in place to the top of the GESS duct.
15
i . .. . .
Figure 4. Radiator Grill Clearance Slot in Adapter A at the Bottom-One Side
* Figure 5. Rubbersized Fiberglass Fabric Patch over Radiator Gril Clearance Slot* in Adapter A for Sealing
4 16
This matter was addressed in the new adapter design by
moving the gasket upward placing it right across the
mounting holes. That necessitates punching holes in the
gasket but it was found that a one inch wide gasket is
adequate to provide proper sealing around the holes.
As with the side mounting flanges of the adapter, spacers
were placed at the top row of mount holes to avoid over-
compression of the gasket and get even spacing of the
adapter from the generator at the top. Without the spacers
it was found that the torque necessary for proper gasket
compression is much less than one normally tightens bolts so
that gasket overcompression is likely. Furthermore, engine
vibration may cause backing out of the bolts if they are
only tightened sufficiently to compress the gasket the
proper amount without spacers anyway. The spacers used
along the top row of mount holes were thinner than the side
spacers because there is already a sheet metal overlap at
the top. Greater compression of the gasket was designed in
there so the plane of the mounting surface of the adapter
was maintained parallel to the main surface of the generator
below the top inch where the overlap occurs.
Figure 6 shows a close-up of the side of the A adapter where
the exhaust extension passes. A cut-out was required forclearance there since the exhaust is so close to the side of
the generator. The figure shows the cut-out. To insure
that the hot exhaust pipe will not contact the aluminum
frame at the side of the adapter, a fiberglass reinforced
standoff was positioned in the cut-out region to act as a
bumper. It protrudes above the depth of cut-out about
1/16th inch so that it will contact the exhaust extension
before the aluminum frame will. Having a thermal conduc-
17
1 'SFigure 6. Cut-out in A Adapter Side Frame for Exhaust Extension Clearance
18
tivity about 1/60th that of aluminum it will avoid the heat
flow to the side of the adapter which would take place if
the exhaust extension were permitted to contact the adapter
side. That contact is potentially a problem because the
position of the exhaust pipe is not closely located with
respect to the clearance hole for the exhaust pipe in the
radiator section skin. The mechanical link follows thechain: exhaust pipe to muffler to engine to engine mounts
to generator base frame to radiator frame to the radiator
section where the clearance hole for the exhaust pipe islocated. That long series of mechanical connections islikely to produce enough uncertainty in exhaust pipe
location to cause the exhaust extension to touch the side of
the A adapter in some cases, and so the insulating bumper
was provided.
2.2 Adapter B Design
2.2.1 Goals for Adapter B
Adapter B is experimental in nature with the basic goal of
mounting the GESS in a down tilted attitude so that none of
the hot interior parts of the GESS can be seen above a
horizontal plane through the tip of the GESS. There might
be, however, secondary heating of the ground due to the
ejection of hot gases downward as a result of this tipping
down of the GESS. The degree of severity of ground heating
or other secondary heating which may result is not known,
and that is why the B adapter is experimental.
This adapter, like adapter A, was to be insulated for
thermal control of surface temperatures. No weight limita-
19
tion was imposed, but similar construction techniques to
those used in making the A adapter were followed so that the
B adapter would be relatively lightweight also.
2.2.2 Description of Adapter B
Figure 7 is a photograph of adapter B latched in place onadapter A. The B adapter is a sheet aluminum weldment
with insulation on the inside very similar to adapter A
insulation. The complete B adapter with insulation and
fastening latches weighs 19.7 kg.
Figure 8 shows the GESS attached to the B adapter. No
opening is exposed above the horizontal. As for the A
adapter a lip or shelf was provided to rest the GESS duct on
during attachment. It should be mentioned that this photo-
graph does not show any blanket or jacketing on the adaptes
although they would be an indispensible part of the suppres-
sion system with the GESS duct. Both adapters must be
covered in the same way as the GESS with blanket or jacket
insulation in addition to that provided inside the metal
skin of the adapters in order to get proper nighttime
thermal suppression.
Insulation inside the B adapter is identical to that in
adapter A except in the top section where an additional
layer of fiberglass insulation is added to build up theinsulation to the same level as for the GESS. Theinsulation is in fact of identical type and thickness to
that in the top of the GESS - one layer one inch thick of
20
-"hf
IFigure 7. Adapter B Latched to Adapter A on I15KW Generator
21
Figure 8. GESS Duct Latched to Adapter B
22
silica/alumina fiber batt (8 lb/ft 3 ) just under the
perforated metal sheet to the inside, and another inch thick
layer of fiberglass batt (3 lb/ft 3 ) next to the outside
skin of the adapter. The reason for use of the silica/
alumina fiber batt to the inside of the adapters is
primarily prevent any possible burning or "punking" of the
insulation in the forced draft environment. There have been
observations of occasional ejection of incandescent
particles from diesel engine exhaust which could ignite
fiberglass insulation if they were to lodge on it.
Since the B adapter mounts directly on the A adapter, where
the GESS duct would mount if the B adapter were not in use,
the same fastening system as for the A adapter and GESS must
be used. Similarly the GESS must mount on the tilted face
of the B adapter so that the fastening system there must
mirror that on the A adapter. Thus the Simmons "link lock"
catch and striker were used again.
2.3 Exhaust Extensions for Use with Adapters A and B
It was found in earlier design work with the GESS system
that an important part of the flow control was redirection
of engine exhaust gases toward the opening of the GESS ductjby means of an exhaust extension. Experience showed that
exhaust impingement on interior surfaces of the GESS ductf ,i caused excessive thermal loading there if allowed.
For the present adapters work analysis indicated that two
1 exhaust extensions would be needed - one for each GESS duct
configuration (normal and tilted down). Figures 9 and 10
show the two exhaust extensions with the angles of bend and
twist which aim the exhaust at the center of the duct
opening.
I23
______.-
Figure 9. Exhaust Extension for Adapter A.
Figure 10. Exhaust Extension for Adapter B.
24
Ia
To force the installer to properly align the exhaust
extensions, a mounting flange at the base of the extensions
was designed with vertical slots which align with two
existing holes in the sheet metal around the exhaust. It
may be necessary to loosen the two mounting bolts holding
the muffler assembly to the engine exhaust manifold so that
the exhaust pipe will move to the proper position for
mounting the exhaust extensions (aligning the two slots with
two holes in the sheet metal face of the generator). With*
the exhaust extension in place the two muffler assembly
mounting bolts should then be retightened.
The A adapter exhaust extension which was built from the
first set of drawings was found to be too short for simple
installation of the GESS duct. Although there is no
interference between the extension and the internal duct
bracing once the duct is in place on the adapter, difficulty
was experienced while maneuvering the duct into place due to
interference with the extension. The drawings were changed
to lengthen the extension one inch before the bend. It is
believed that this change will alleviate the installation
problem.
2.4 GESS Duct Design Modifications for Compatibility with
Adapters
The GESS duct itself was also modified in the drawings forcompatibility with the A and B adapters. As a consequence
of making the A adapter thin, the fastening catch, which was
centered on the thinner adapter, was moved 0.40 inch closer
to the GESS duct than was the case before. So the matingpart (striker) on the GESS duct had to be moved back. That
required relocation of the holes for mounting the striker
25
II
• i0'
*o i~-w -
and increase in the size of the clearance cut-out in the
side skin of the GESS duct at the bottom. At the top of
the GESS duct no direct changes in the basic form were
needed but the striker plate (plate on which the strikers
for vertical and down pull are placed) was changed to
accomodate the move back. Therefore, this different striker
plate assembly must be used at the duct top to make the GESS
fasteners compatible with the new adapters. That plate is
also moved upward by one set of the holes in the side of the
GESS duct frame to the top set of holes (4.5 inch apart).
Those holes already exist so no new holes are needed at the
top to mount the modified striker plate assembly on the GESS
duct.
A little strengthening of the striker plate was built in
after observation of bending during attachment of the GESS
when the down pull latch was secured. The plate was widened
slightly and a radius added at the plate corner at the bend.
2.5 GESS Blanket Design
2.5.1 GESS Blanket and Duct Jacket Changes
Several factors were involved in the need for blanket design
changes. One was that the use of adapter A pulls the
blanket which covers the generator forward by the thicknessof the adapter. In addition, it had been found in pasttesting that the large generator blanket was not long enough
to cover the rear most portions of the generator which are
warm. Tests had also shown that the side cover jacket
sections for the GESS duct were not sufficiently insulative.
They needed to be made thicker to increase the resistance to
* heat transfer.
26
Finally, there were two difficulties with the area below the
duct. The large generator blanket up to now has had two ear
flaps sewn on which fold around the generator once the
blanket is draped over the generator and link together in
front of the battery compartment door to cover them. Sewing
effects however were found to cause position errors in the
ear locations which made the fit to the generator poor.
There had also been a problem with clearance for the battery
compartment doors to open past the bottom panel of the GESS
duct jacket. Both these difficulties it was felt could be
addressed by eliminating the ears on the large blanket and
lengthening the bottom duct jacket so that it bent around to
cover the battery compartment doors in place of the blanket
ears. The bottom duct jacket panel would then be simply
removed to access the batteries.
Then there was the new jacketing system which was required
for the B adapter so that it may be used as an independent
section with the GESS blanket and duct jacket system.
Changes to the large generator blanket were the elimination
of the ears, increasing the length from 56 to 63 inches, and
the placement of a two inch wide loop tape attaching flap
along the entire front (toward the GESS duct) edge of the
blanket. This flap with loop tape on the forward edge serves
to attach the blanket to hook tape on the duct (or B
adapter) jacket and to hook tape on the bottom panel of the
GESS duct jacket where it bends down to cover the battery
compartment doors. The large blanket thus becomes simpler.
It is just a rectangle with an attaching flap all along one
I edge.Use of the GESS duct bottom jacket panel to cover the
battery compartment doors required that it be readily
removable to provide access to the batteries. In prior use,
it had been attached with hook and loop tape directly to the
27
1 .J ______.. .."
metal skin of the GESS duct and then the side jacket panels
for the duct attached over the top of the bottom jacket
panel. The necessary changes in attachment were made so
that the side jacket panels attach directly to the metal
GESS duct and the bottom jacket panel attaches outside of
the side jacket panels and is therefore, easily removablewhen the batteries must be serviced. It was also extendedin length so that it will cover the battery compartment
doors as discussed before.
Modifications to the duct side jacket panels were made tomake the attachment shift from over to under the bottom
jacket panel and to enclose one added layer of 1/4 inch
thick insulation foam. Hook tape for attaching the large
generator blanket was also lengthened for more secure
fastening of the blanket, to the GESS duct jacket.
2.5.2 B Adapter Jacket Design
Three jacket pieces were also designed for use with the
triangular B adapter. They are made in much the same
construction as the GESS jacket pieces with size and shape
changes to fit the B adapter. The same number of insulation
layers was used as for corresponding pieces of the duct
jacket. Hook tape was provided where needed so that the
blanket will attach to the B adapter jacket in much the same
way it attaches to the GESS jacket pieces. The B adapter
jacket was made in sections because the thickness required
for proper insulation is not compatible with the tight bends• I needed to fit the adapter if the jacket were made in a
single piece. That is basically the same reason the GESS
duct jacket was made in four sections.
.2
2.6 Acoustic Tests on the Adapters with the GESS Duct and
Blanket
The generator which was supplied to Varo for use with the
GESS and adapters was a 15 kw diesel driven set which had
been modified by Industrial Acoustics Corp. for noise
control features. Side doors for access to the generator
and engine sections were replaced with thicker insulated
doors faced with perforated metal inside. Short panels
below the doors were also treated the same way. The air
intake grill was also replaced with,silencing louver.
The generator was fitted with adapters, GESS duct and
blanket for acoustic testing and the generator situated in
the door of the storage building in which it was housed.
Electrical load was maintained at 70% or 100% while sound
pressure levels were measured at 25 feet from the generator.
The measuring instrument was a GenRad model 1982 Precision
Sound Level Meter and Analyzer. Figures 11 and 13 depict
the site and give results in dBA.
It may be noted that the measurement situation was not
optimum from several aspects. First, the siting of the
generator partially inside a building could have affected
the reading. It was not trailer mounted and therefore, was
just about four inches off the floor. The asphalt road infront of the generator may also have increased readings
somewhat, asphalt being a more acoustically live surface
than grass. However, all measurements were well below the
80 dBA limit stated in the contract with either the A
14adapter and GESS duct or with both adapters and the GESS
duct for both tests.
1 29
building with concrete ftoo
15kw generao withNoise h/R Control Kit
dorGESS blanket
macrte walk A adapxter, GElS and Jacket
Q -elcal load barrell
bush 25ft. AP450 OR
~(BOeet I1 fromgenerator) 5t
aphalt road
76.0 72.7
Note: All readings In dSA from GiR 1982 meter
Figure 11. Sound Pressure Level Readints for Generator with A adapter and GESS, Generatorat 70% Lead. Test Run on 4/18/80.
30
building with concrete floor
15kw generator with
GESSblaketNoise h/R Control Kit
door
concrete walk A adapter, GESS and Jacket
(1)-electrical load barrel
bush 45t0 45
(80ls at 1O' from 25ft.Sgeneratorl
asphalt road
~lj Note: All readings in dSA from GA 1962 meter
Figure 12. Sound Proasure Level Readings for Generator with A Adapter and GESS.Generator Load 100%. Test Run 4/18/80.
31
building with concrete floor
15kw generator withNoise I/R Control Kit
GUSS blanket
door _ _ _ _
concrete walk A and B adapters, GESS and jacket
electical load barrel
bush 25ft. ^0450 4
(80 t 12' from 25ft.generator)I
asphalt roadI
75.5 72.5
75.5.
Figure 13. Sound Presure Level Reading. for Generator with A and B Adaptes andGESS. Generator at 100% Load. Ts Run on 4/18/80.
32
Iwa
On the basis of this testing, it is projected that the
adapters perform satisfactorily in regard to acoustic
suppression with the GESS kit on the 15 kw generator asmodified with the acoustic suppression doors, side panels
and louver air intake.
i
f [
• 33
3.0 DISCUSSION
Dimensional difficulties were experienced when the first
parts were received from the vendor. Then it was
ascertained that the pattern adapter drawing from which
mounting hole locations were taken for design of the new
adapter was in error although the adapter supplied to Varo
had a correct hole pattern for mounting. The pattern
adapter however, was prepared with gasketing on both sides
and the supplied GESS duct had no gasket at all. That
affected the sealing relationship between the A adapter and
the GESS duct since the gasket must be applied to the duct
(as required for compatibility with 60 kw diesel
generators). Different areas were used for sealing when the
pattern adapter was joined to the duct compared to the case
in which the gasket is attached to the GESS duct and thenmated to the new adapter. That resulted in the A adapter
being slightly too short for optimum sealing to the GESS
duct although the seal is adequate. Therefore, no change
was made in the adapter furnished at the end of the
contract, but modification to the drawings for the A adapter
were made to increase the height for optimum seal.
Another difficulty was noted with the A adapter in frame
squareness and twist. Notes were added to the drawings to
control those factors. It is probable that some of this
problem developed when four gussets were welded into the A
adapter frame after having been accidentally omitted by the
vendor for the first delivery.
Since there has been more than one GESS duct design during
dvelopment of the GESS, is should be kept clear that the
present adapters are designed to be compatible with the
* 34
• I
• i.
latest GESS duct design resulting from contract DAAK70-77-M-
4985 in 1978 (after the modifications indicated in section
2.4 of this report have been made). The duct supplied to
Varo was not one of those although the differences are not
great. The area of difference which causes some problem is
the location of bolts on the bottom of the duct frame. Bolt
heads of the duct were supposed to drop into holes provided
in the B adapter lip put there to assist the duct installer.The lip is designed into the B adapter as in the A adapter
to help support the weight of the GESS duct while it is
being latched. Because of the slant at which the duct is
mounted there was some concern that the duct bottom might
slip forward off the lip and that is the reason why holes
were placed in the lip. They were to allow the bolt heads
protruding from the bottom of the duct to drop into the lip
and prevent the duct from slipping off the lip. That
objective could not be properly evaluated since the GESS
duct provided has the holes in a different location from
those in the lip (designed for the newer duct). There did
not seem to be any special difficulty in holding the duct in
place, however, without the assistance of the holes over the
bolt heads, so that feature may possibly be omitted.
One fact it is felt must be emphasized is that the blanket
and jacket sections are not optional parts of the GESS
system. Insulation provided inside the metal skin of the
GESS duct and the adapters is not sufficient to presentsurface temperatures near enough to ambient levels foradequate thermal suppression. The blanket and jacket
sections must be in place on the exterior for proper
nighttime thermal control.
35
-0-
4.0 CONCLUSIONS
The two adapters which were designed and built under this
contract meet the original goals for performance
mechanically and acoustically. The A adapter weighs about
30% less than the weight limit set at the beginning of the
effort. Both adapters are readily installable by one man.
The A adapter mounts to 15 kw or 30 kw diesel generators
which have the same radiator/exhaust configuration as the
MEP 113A (NSN 6115-00-118-1244) 15 kw generator by removing
13 bolts. It is not necessary to drill any holes or remove
the radiator grill for this installation. Only the exhaust
weather cap must be removed to install an exhaust extension.
The B adapter mounts to the A adapter in quick release
fashion just as the GESS duct attaches. Both adapters
provide a resting lip upon which to set the base of the GESS
duct to facilitate attachment. Sealing around the
interfaces between adapter A and the generator, between A
and B adapters, and between the B adapter and the GESS duct
is good allowing no significant hot air leakage so that all
exhaust flows are ejected out the designed opening in the
GESS duct.
436,
-- zz i i .. . . = _ _= _ = .. ....... ____________________
5.0 RECOMMENDATIONS
Thermal testing is needed to invesigate whether the
resistance to heat transfer afforded by the insulated
adapters is adequate for thermal suppression effect. It
must be noted that this testing must include blanket and
jacket sections for all items in the test - i.e. blanket and
GESS jacket with the A adapter and GESS duct, and blanket, Badapter jacket, and GESS jacket with the A and B adapters
and GESS duct.
Secondary heating effects from the exhaust stream should beinvestigated with the generator in its normal position for
various wind conditions - no wind, wind opposing the exhaust
flow and wind aiding the exhaust flow (exhaust with the
wind).
Should any production of GESS ducts be entered into in the
future, the changes in fastening on the sides of the duct
which are discussed in section 2.4 of this report should be
made if compatibility with the adapters developed in this
effort is desired.
37
II * h W ~ e n e- - r .~a. .ft~j ... ,.a
Distribution List
Addressee Copies
CommanderU.S. Army Mobility Equipment Research
adDevelopment CommandFotBeivoir, Virginia 22060
At:DRDME-RT 4/1DRDME-WC 2DRDME- TQ1DRDAR-TSB-S1
Defense Technical Information Center 2
Attn: DTIC-MCameron StationAlexandria, Virginia 22314